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The melatonin receptor subtype MT 1 is expressed in human gallbladder epithelia
Author(s) -
Aust Sylvia,
Thalhammer Theresia,
Humpeler Susanne,
Jäger Walter,
Klimpfinger Martin,
Tucek Gerhard,
Obrist Peter,
Marktl Wolfgang,
Penner Edward,
Ekmekcioglu Cem
Publication year - 2004
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1046/j.1600-079x.2003.00095.x
Subject(s) - gallbladder , melatonin , messenger rna , western blot , melatonin receptor , biology , blot , gallbladder stone , immunofluorescence , medicine , endocrinology , antibody , gene , immunology , biochemistry
Based on the fact that human bile and, particularly gallbladder bile, contains high physiological levels of the antioxidant melatonin, the aim of this study was to investigate whether the melatonin receptor MT 1 is present in human gallbladder. Expression and localization of MT 1 was assessed by RT‐PCR, Western blotting and immunofluorescence analysis in gallbladder samples from patients with cholelithiasis and with advanced gallbladder carcinoma. Additionally, we monitored mRNA expression of the two key enzymes of melatonin synthesis, i.e. arylalkylamine‐ N ‐acetyltransferase (AANAT) and hydroxyindole‐ O ‐methyltransferase (HIOMT). MT 1 mRNA and protein were present in all cholelithiasis (n = 10) and gallbladder carcinoma (n = 5) samples. As indicated from RT‐PCR and Western blot studies, MT 1 is located in gallbladder epithelia. Epithelial expression was further proven by immunofluorescence staining of MT 1 in paraffin‐embedded cholelithiasis and gallbladder carcinoma sections. Analysis of AANAT and HIOMT mRNA expression showed that HIOMT mRNA is present in gallbladder. Surprisingly, AANAT was not detectable under conditions where it was found in a human colon specimen. The absence of AANAT suggests that in human gallbladder, HIOMT might be involved in the formation of 5‐hydroxytryptamine products other than melatonin. In summary, our results provide the first evidence for the presence of MT 1 in human gallbladder epithelia. Therefore, in addition to its profound antioxidative effects in the biliary system, melatonin might also act through MT 1 ‐mediated signal transduction pathways. Thereby, it might be involved in the regulation of gallbladder function.